Cyproheptadine for pediatric intrathecal baclofen withdrawal: a case report

Spinal motoneurons respond aberrantly to serotonin in a rabbit model of cerebral palsy

Cerebral palsy (CP) is caused by a variety of factors that damage the developing central nervous system. Impaired motor control, including muscle stiffness and spasticity, is the hallmark of spastic CP. Rabbits that experience hypoxic-ischaemic (HI) injury in utero (at 70%-83% gestation) are born with muscle stiffness, hyperreflexia and, as recently discovered, increased 5-HT in the spinal cord. To determine whether serotonergic modulation of spinal motoneurons (MNs) contributes to motor deficits, we performed ex vivo whole cell patch clamp in neonatal rabbit spinal cord slices at postnatal day (P) 0-5. HI MNs responded to the application of α-methyl 5-HT (a 5-HT1 /5-HT2 receptor agonist) and citalopram (a selective 5-HT reuptake inhibitor) with increased amplitude and hyperpolarization of persistent inward currents and hyperpolarized threshold voltage for action potentials, whereas control MNs did not exhibit any of these responses. Although 5-HT similarly modulated MN properties of HI motor-unaffected and motor-affected kits, it affected sag/hyperpolarization-activated cation current (Ih ) and spike frequency adaptation only in HI motor-affected MNs. To further explore the differential sensitivity of MNs to 5-HT, we performed immunostaining for inhibitory 5-HT1A receptors in lumbar spinal MNs at P5. Fewer HI MNs expressed the 5-HT1A receptor compared to age-matched control MNs. This suggests that HI MNs may lack a normal mechanism of central fatigue, mediated by 5-HT1A receptors. Altered expression of other 5-HT receptors (including 5-HT2 ) likely also contributes to the robust increase in HI MN excitability. In summary, by directly exciting MNs, the increased concentration of spinal 5-HT in HI-affected rabbits can cause MN hyperexcitability, muscle stiffness and spasticity characteristic of CP. Therapeutic strategies that target serotonergic neuromodulation may be beneficial to individuals with CP. KEY POINTS: We used whole cell patch clamp electrophysiology to test the responsivity of spinal motoneurons (MNs) from neonatal control and hypoxia-ischaemia (HI) rabbits to 5-HT, which is elevated in the spinal cord after prenatal HI injury. HI rabbit MNs showed a more robust excitatory response to 5-HT than control rabbit MNs, including hyperpolarization of the persistent inward current and threshold voltage for action potentials. Although most MN properties of HI motor-unaffected and motor-affected kits responded similarly to 5-HT, 5-HT caused larger sag/hyperpolarization-activated cation current (Ih ) and altered repetitive firing patterns only in HI motor-affected MNs. Immunostaining revealed that fewer lumbar MNs expressed inhibitory 5-HT1A receptors in HI rabbits compared to controls, which could account for the more robust excitatory response of HI MNs to 5-HT. These results suggest that elevated 5-HT after prenatal HI injury could trigger a cascade of events that lead to muscle stiffness and altered motor unit development.

Spinal motoneurons respond aberrantly to serotonin in a rabbit model of cerebral palsy

Cerebral palsy (CP) is caused by a variety of factors that damage the developing central nervous system. Impaired motor control, including muscle stiffness and spasticity, is the hallmark of spastic CP. Rabbits that experience hypoxic-ischemic (HI) injury in utero (at 70-80% gestation) are born with muscle stiffness, hyperreflexia, and, as recently discovered, increased serotonin (5-HT) in the spinal cord. To determine whether serotonergic modulation of spinal motoneurons (MNs) contributes to motor deficits, we performed ex vivo whole cell patch clamp in neonatal rabbit spinal cord slices at postnatal day (P) 0-5. HI MNs responded to application of α-methyl 5-HT (a 5-HT 1 /5-HT 2 receptor agonist) and citalopram (a selective 5-HT reuptake inhibitor) with hyperpolarization of persistent inward currents and threshold voltage for action potentials, reduced maximum firing rate, and an altered pattern of spike frequency adaptation while control MNs did not exhibit any of these responses. To further explore the differential sensitivity of MNs to 5-HT, we performed immunohistochemistry for inhibitory 5-HT 1A receptors in lumbar spinal MNs at P5. Fewer HI MNs expressed the 5-HT 1A receptor compared to age-matched controls. This suggests many HI MNs lack a normal mechanism of central fatigue mediated by 5-HT 1A receptors. Other 5-HT receptors (including 5-HT 2 ) are likely responsible for the robust increase in HI MN excitability. In summary, by directly exciting MNs, the increased concentration of spinal 5-HT in HI rabbits can cause MN hyperexcitability, muscle stiffness, and spasticity characteristic of CP. Therapeutic strategies that target serotonergic neuromodulation may be beneficial to individuals with CP.

Key points

After prenatal hypoxia-ischemia (HI), neonatal rabbits that show hypertonia are known to have higher levels of spinal serotoninWe tested responsivity of spinal motoneurons (MNs) in neonatal control and HI rabbits to serotonin using whole cell patch clampMNs from HI rabbits showed a more robust excitatory response to serotonin than control MNs, including hyperpolarization of the persistent inward current and threshold for action potentials, larger post-inhibitory rebound, and less spike frequency adaptation Based on immunohistochemistry of lumbar MNs, fewer HI MNs express inhibitory 5HT 1A receptors than control MNs, which could account for the more robust excitatory response of HI MNs. These results suggest that after HI injury, the increased serotonin could trigger a cascade of events leading to muscle stiffness and altered motor unit development.

Principles of Pharmacotherapy of Seizures and Status Epilepticus

Status epilepticus is a neurological emergency with an outcome that is highly associated with the initial pharmacotherapy management that must be administered in a timely fashion. Beyond first-line therapy of status epilepticus, treatment is not guided by robust evidence. Optimal pharmacotherapy selection for individual patients is essential in the management of seizures and status epilepticus with careful evaluation of pharmacokinetic and pharmacodynamic factors. With the addition of newer antiseizure agents to the market, understanding their role in the management of status epilepticus is critical. Etiology-guided therapy should be considered in certain patients with drug-induced seizures, alcohol withdrawal, or autoimmune encephalitis. Some patient populations warrant special consideration, such as pediatric, pregnant, elderly, and the critically ill. Seizure prophylaxis is indicated in select patients with acute neurological injury and should be limited to the acute postinjury period.

Baclofen Pumps: Uses and Complications

Intrathecal baclofen therapy, given via an implanted pump in the abdominal wall either as a continuous infusion or bolus dosing, has been used for more than 25 years to treat the spasticity and dystonia associated with various brain and spinal cord conditions. Pediatric clinicians occasionally encounter baclofen pumps, and in the pediatric setting, significant morbidity can arise from their use. This article presents the background, mechanism of action, uses, and complications of intrathecal baclofen therapy and discusses various management strategies should complications occur.

Baclofen in the Therapeutic of Sequele of Traumatic Brain Injury: Spasticity

Traumatic brain injury (TBI) is an alteration in brain function, caused by an external force, which may be a hit on the skull, rapid acceleration or deceleration, penetration of an object, or shock waves from an explosion. Traumatic brain injury is a major cause of morbidity and mortality worldwide, with a high prevalence rate in pediatric patients, in which treatment options are still limited, not available at present neuroprotective drugs. Although the therapeutic management of these patients is varied and dependent on the severity of the injury, general techniques of drug types are handled, as well as physical and surgical. Baclofen is a muscle relaxant used to treat spasticity and improve mobility in patients with spinal cord injuries, relieving pain and muscle stiffness. Pharmacological support with baclofen is contradictory, because disruption of its oral administration may cause increased muscle tone syndrome and muscle spasm, prolonged seizures, hyperthermia, dysesthesia, hallucinations, or even multisystem organ failure. Combined treatments must consider the pathophysiology of broader alterations than only excitation/inhibition context, allowing the patient's reintegration with the greatest functionality.

Dexmedetomidine for acute baclofen withdrawal

BACKGROUND

Intrathecal baclofen is widely accepted as a treatment option for severe spasticity through its γ-Aminobutyric acid-B (GABAB ) agonist properties. Abrupt cessation can lead to severe and life-threatening withdrawal characterized by altered mental status, autonomic dysreflexia, rigidity, and seizures. This symptomatic presentation is similar to alcohol withdrawal, which is mediated by modification of GABAA expression. Use of the α2-adrenergic agonist dexmedetomidine for the treatment of ethanol withdrawal has been widely reported, raising the question of its potential role in baclofen withdrawal. We present a case of the successful treatment of acute severe baclofen withdrawal with a dexmedetomidine infusion.

METHODS

A 15-year-old patient with spastic quadriparesis and cerebral palsy underwent unexpected removal of his baclofen pump due to an infection that was encountered during a planned pump revision. Following removal, he was placed on high dose enteral baclofen every 6 h. Despite further benzodiazepine supplementation, he had progressive hemodynamic instability, severe rebound spasticity, and intermittent spontaneous clonus consistent with baclofen withdrawal. A dexmedetomidine infusion was titrated to a peak dose of 16 mcg per hour with successful treatment of withdrawal symptoms.

RESULTS

The patient became normotensive without tachycardia. Tone and agitation improved.

CONCLUSION

Dexmedetomidine is to our knowledge a previously unreported option for treatment of acute severe baclofen withdrawal. We report a case of safe and efficacious use in a patient with spastic quadriparesis on chronic intrathecal baclofen. Scientifically rigorous comparison with other options remains to be performed.

Acute intrathecal baclofen withdrawal: a brief review of treatment options

BACKGROUND

Acute baclofen toxicity and withdrawal can present with a constellation of symptoms making differentiation between these two entities and other potential diagnoses challenging. Baclofen withdrawal is associated with numerous complications which may require neurocritical care expertise such as respiratory failure, refractory seizures, delirium, and blood pressure lability.

METHODS

Case report and literature review.

RESULTS

This case report discusses a case of intrathecal baclofen (ITB) withdrawal, focusing on the differential diagnosis for acute baclofen withdrawal and reviews the various options that exist to treat the symptoms of acute baclofen withdrawal such as benzodiazepines, propofol, skeletal muscle relaxants, and tizanidine.

CONCLUSIONS

Critical care practitioners should be prepared to treat this potentially devastating and often refractory complication of ITB therapy.

Status dystonicus resembling the intrathecal baclofen withdrawal syndrome: a case report and review of the literature

Introduction

Status dystonicus is a rare but life-threatening disorder characterized by increasingly frequent and severe episodes of generalized dystonia that may occur in patients with primary or secondary dystonia. Painful and repetitive spasms interfere with respiration and may cause metabolic disturbances such as hyperpyrexia, dehydration, respiratory insufficiency, and acute renal failure secondary to rhabdomyolysis. Intrathecally administered baclofen, delivered by an implantable pump system, is widely used for the treatment of refractory spasticity. Abrupt cessation of intrathecal baclofen infusion has been associated with a severe withdrawal syndrome comprised of dystonia, autonomic dysfunction, hyperthermia, end-organ failure and sometimes death. The aetiology of this syndrome is not well understood. Status dystonicus describes the episodes of acute and life-threatening generalized dystonia, which occasionally manifest themselves in patients with dystonic syndromes.

Case presentation

We present the case of a nine-year-old Caucasian boy who experienced a severe episode of status dystonicus with no known cause and clinical features resembling those described in intrathecal baclofen withdrawal. Our patient subsequently underwent the placement of an intrathecal baclofen pump without incident.

Conclusion

The similarity between the clinical features of the case we present and those reported in connection to abrupt withdrawal of intrathecal baclofen is emphasized. Several drugs, although not intrathecal baclofen withdrawal, have previously been associated with status dystonicus. The similarity between the life-threatening dystonic episode experienced by our patient, and those reported in intrathecal baclofen withdrawal, highlights the possibility that, rather than representing a true physiological withdrawal syndrome, abrupt withdrawal of intrathecal baclofen may simply precipitate an episode of status dystonicus in susceptible individuals. The clinical similarities between the intrathecal baclofen withdrawal syndrome and status dystonicus have not previously been highlighted.

Adverse drug reactions resulting in hyperthermia in the intensive care unit

Hyperthermia is frequently seen in the intensive care setting and is associated with significant morbidity and mortality. It is often initially misdiagnosed as fever associated with infection. Atypical presentations of classic syndromes are common. Clinical suspicion is the key to diagnosis. Adverse drug reactions are a frequent culprit. Syndromes include adrenergic "fever," anticholinergic "fever," antidopaminergic "fever," serotonin syndrome, malignant hyperthermia, uncoupling of oxidative phosphorylation, and withdrawal from baclofen. This review describes the pathophysiology of hyperthermia, as distinct from fever, and the physiology, diagnosis, and treatment of serotonin syndrome, neuroleptic malignant syndrome, malignant hyperthermia, and baclofen withdrawal. Much of the available evidence regarding the treatment of these disorders is based on single case reports, case series, or animal models. Therapeutic modalities consist of identification/withdrawal of possible offending agent(s), support directed at lowering temperature and preventing/treating complications, as well as targeted pharmacologic therapy directed at the specific cause. Early recognition and treatment using a multidisciplinary approach are essential to achieve the best possible outcome.

Consensus on the appropriate use of intrathecal baclofen (ITB) therapy in paediatric spasticity

Among features of motor disorders in children, spasticity is associated with considerable morbidity and problems in care, particularly in severely affected patients. Intrathecal baclofen (ITB) has been increasingly used as a relatively specific treatment modality for spasticity. To date, most of the evidence for its use in paediatric patients has come from retrospective and uncontrolled studies, although randomised, controlled trials of screening ITB and ITB therapy itself have recently been published. This consensus statement on the use of ITB in paediatric patients with spasticity was developed on the basis of currently available evidence, with the aim of providing information for clinicians, promoting an expert opinion and a consistent approach to the management of these patients and emphasising the need for further prospective, large-scale studies.